update to nuxt 4

app/composables/user.ts

@@ -0,0 +1,13 @@
+import type { UserModel } from "~~/prisma/client/models";
+
+// undefined = haven't check
+// null = check, no user
+// {} = check, user
+
+export const useUser = () => useState<UserModel | undefined | null>(undefined);
+export const updateUser = async () => {
+  const user = useUser();
+  if (user.value === null) return;
+
+  user.value = await $dropFetch<UserModel | null>("/api/v1/user");
+};